The first four ionization energies for element X (not in kJ/mol) are 170, 350, 1800, 2500. The first four ionization energies for element Y are 200, 400, 3500, 5000. Identify elements X and Y. (There may be more than one correct answer)
The ionization energies jump abruptly after the first two electrons have been removed in both cases. These means that the elements are in the second group. The ionization energy also decreases when going down a group so element Y is above group X in the periodic table. A possible solution: Y = Magnesium X = Calcium
